I have started mixing in the chick crumbs and so far I am happy with them, ie neither Jaffa nor Mosi has noticed anything different (eg smell) and happy to use the tray with a mix of wbcl and chick crumbs. The ones from pah work out cheaper than buying wbcl, even from zooplus, so for now I will use them and if everything goes ok, I'll then look into ordering some cheaper online.